1. Field of the Invention
The present invention relates to insulating glass panels or the like and more particularly to an improved panel construction and method of panel fabrication.
Insulating glass panels of the sort commonly used as glazing in windows and doors are normally constructed by sandwiching a spacer frame assembly between sheets of glass, or equivalent material, and hermetically bonding the sheets to the spacer frame assembly. A finished panel is typically square or rectangular with the spacer frame assembly extending completely about and immediately adjacent the outer periphery. The panel can then be installed in a suitable supporting structure (such as a window frame) which masks the spacer frame assembly from view and enables the panel to be installed in a larger structure, such as an exterior building wall.
As its name implies the spacer frame assembly functions to space the glass sheets apart and thus provide an insulative "dead air" space between them. It is essential in such panels that the spacer frame assembly be and remain hermetically attached to the glass sheets throughout the expected life of the panel. If the air space between the glass sheets is not hermetic, atmospheric water vapor will eventually infiltrate the dead air space and inevitably, under appropriate atmospheric conditions, condense on the glass surfaces bounding the dead air space. While the presence of water vapor in the dead air space does not materially reduce the insulative effectiveness of the panel, condensation on the glass in the space "fogs" the glass, cannot be removed and the utility of the panel as a window is adversely affected. Moreover, repeated condensation and evaporation of such moisture within the panels results in the windows becoming permanently stained and unsightly even when there is no condensation in the panel.
2. The Prior Art
In order to assure a hermetic bond between the spacer frame and the glass sheets a mastic-like sealant material has been applied to opposite sides of the spacer frame continuously about the panel. A typical sealant material, known in the industry as a Butyl "hot melt" adhesive, is applied to the spacer frame, the spacer frame assembly is sandwiched between the glass sheets, and the panel is subjected to high energy radiant heating while the glass sheets are pressed against the spacer frame assembly. The sealant is heated sufficiently to "melt" and flow into sealing and bonding contact between the glass and the spacer frame. Upon cooling, and in use, the sealant material is relatively rigid although it does tend to exhibit plastic flow characteristics under stress.
In use the insulating glass panels are subjected to appreciable temperature differentials and to frequent temperature "cycling." The spacer frames therefore have been subjected to stresses and strain resulting from temperature induced differential expansion and contraction. In panels where the spacer frame segments were not firmly secured together, the applied stresses sometimes resulted in the frame segments shifting apart and causing the sealant material to deform sufficiently to break the seal between the frame and the glass. While the structural integrity of the panels was not usually adversely affected, the broken seals permitted migration of atmospheric moisture into the dead air space.
Accordingly the use of corner connectors between spacer frame segments for securing the segments together and rigidifying the corners was proposed. The corner connectors were usually formed of relatively rigid plastic or zinc alloy materials and when attached to the frame segments provided sufficient strength to maintain the integrity of the spacer frame assembly.
Even though insulating glass panel components were hermetically bonded together and the seal remained intact, atmospheric moisture was trapped in the air space when the panels were being assembled. The trapped air-borne moisture often condensed within the panels. In order to avoid this problem the prior art proposed the use of tubular spacer frame segments containing particulate desiccant material. The spacer frame segments were constructed from aluminum or galvanized sheet steel and formed with slightly open interiorly facing seams which permitted the segments to "breathe," i.e., the seams enabled communication between the desiccant material and the panel air space while preventing loss of desiccant into the air space. The desiccant material was effective to dehumidify the air trapped in the panel air space.
The construction of the spacer frames and panels was complicated by the use of desiccant materials in the frame segments. In order to prevent dumping the desiccant material out of the frame segments the frame segments were filled with desiccant material and assembled together using corner connectors which both plugged the ends of the frame segments and formed the spacer frame corners.
Applying the sealant material to the spacer frame was accomplished by moving one side of the spacer frame past two or more sealant extrusion nozzles at a controlled rate of travel and repeating the process for each side of the polygonal spacer frame.
The spacer frame assembly thus formed had a doubled layer of the sealant at each corner of the frame. These layers had to be manually smoothed out and feathered into the single sealant layers adjacent the frame corners to assure that an effective seal could be provided with the glass sheets.
This assembly process was most effectively performed by using two sealant extrusion machines with an operator for each machine being responsible for applying the sealant to the frames. The frame assemblies from each extrusion machine were then placed on a respective table where a finishing operator smoothed the sealant at the corners. An inspector was usually present to inspect the frame assemblies after the finishing operators had completed their ministrations.
Assembly of the panels was then completed in the manner described previously.
The spacer frame assembly process was relatively slow because of the multiple step sealant applying procedure. The extrusion machine had to be started and stopped repeatedly during the application of sealant to a single spacer frame and the sealant was usually applied at a relatively low application rate. Furthermore, application of the coatings was often difficult and cumbersome for the extrusion machine operator, particularly when large size frames had to be coated. For example, when spacer frames for sliding glass door panels were coated, the frames themselves were sometimes six feet long, or longer, per side and although the frame segments were securely connected together, the frames were still quite flexible and thus extremely difficult for the operator to manipulate.
The assembly process was labor intensive and therefore costly since five persons were required to produce spacer frame assemblies insulating glass panel production equipment. It should be noted that spacer frames cannot effectively be produced and stockpiled for eventual use without risking loss of effectiveness of the desiccant material in the frame segments before final assembly of the panels.